1. Field of the Invention
Apparatuses and a method consistent with aspects of the present invention relate to a light scanning unit having a structure of reciprocating scanning light in forward and reverse directions, an image forming apparatus having the same, and a method of synchronizing signal calibrating of the light scanning unit, and more particularly, to a light scanning unit capable of correcting an alignment error between a forward direction scanning line and a reverse direction scanning line, an image forming apparatus having the same, and a method of synchronizing signal calibrating of the light scanning unit.
2. Description of the Related Art
In general, a light scanning unit is employed in an image forming apparatus such as a laser printer, a digital copier, a facsimile, a barcode reader, etc. The image forming apparatus employing the light scanning unit forms a latent image on an image carrying body through a main scanning by a beam deflector, and a sub scanning by driving of the image carrying body.
The light scanning unit includes a light source generating and emitting a light beam having a predetermined wavelength, and a beam deflector deflecting the emitted light beam. The beam deflector is classified into a rotation type using a rotating body such as a rotating multi surface mirror or a hologram disk to deflect an entering light beam in a direction, and a resonance mirror type using a resonance mirror reciprocatingly rotating in a predetermined angle to reciprocatingly scan an entering light beam in forward and reverse directions.
Unlike in the use of a rotation mirror type, with the resonance mirror type, because the light beam is scanned in the forward direction and the reverse direction when an image signal is applied to the light source, it is important that the light scanning unit of the resonance mirror type correctly determines whether the scanning direction of the light beam is the forward direction or the reverse direction. In the light scanning unit of the resonance mirror type, all of a forward direction scanning line and a reverse direction scanning line is used in order to make the most use of the property of a resonance mirror. Here, if there is an alignment error between the forward direction scanning line and the reverse direction scanning line, an image may be distorted by a scanning line unit. Accordingly, it is necessary to correct an alignment between the forward direction scanning line and the reverse direction scanning line.
If an alignment error between the forward and reverse direction scanning lines of the light scanning unit of the resonance mirror type is to be corrected by a firmware, it is difficult to correct an assembling tolerance caused in manufacturing the light scanning unit and a change of a resonance frequency of the resonance mirror due to an internal temperature increase.